We propose to develop a novel method for the diagnosis of Helicobacter pylori. The diagnosis of H. pylori infection is a high medical priority because: this bacterium infects approximately 50% of the world's population; causes peptic ulcer disease, gastric adenocarcinoma, mucosa-associated lymphoid tissue lymphoma and likely several other diseases; and is treatable with antibiotics but if this organism is not eradicated, patients remain at risk for serious complications. Of the many diagnostic tests for H. pylori, the urea breath test (UBT) is the best: it is simple, noninvasive, has excellent sensitivity and specificity and can diagnose current infection. It is based on the ability of H. pylori to convert urea to CO2 and ammonia using its enzyme urease. Current embodiments of UBT employ 13C-urea or the radioactive 14C- urea and detect labeled CO2 in breath. The radioactive UBT is rarely used. Current non- radioactive UBTs are not extensively used because they are costly and not available at the point of care. We propose to develop a simple UBT using as a substrate unlabeled urea and detecting ammonia in breath with a nanosensor incorporated in a very simple device. In this revised application, we have addressed the concerns of the previous reviewers and present extensive preliminary data demonstrating the feasibility of our approach. They include a sensor with appropriate sensitivity and specificity and development of a prototype device. Our specific aims are to 1) Optimize our nanosensor for the determination of ammonia levels in breath air, and 2) Develop a prototype device for the determination of ammonia in breath. The proposed UBT will be simple, inexpensive, noninvasive and available at the point-of-care. Thus it will make widely available a simple device for the diagnosis of H. pylori and the monitoring of treatment efficacy. Our method has the potential to impact human health in an immediate, direct and major way and generate a commercially viable product. PUBLIC HEALTH RELEVANCE: We propose to develop a simple-to-use and inexpensive device to diagnose rapidly infection with of Helicobacter pylori. This organism infects approximately 50% of the world's population and causes peptic ulcer and gastric cancer. The device's impact on public health will be immediate and major. [unreadable] [unreadable] [unreadable]